ACA Marketplace: Nov 1, 2026 – Jan 15, 2027
Medicare AEP: Oct 15 – Dec 7, 2026
Medicare Advantage OE: Jan 1 – Mar 31, 2027
ACA Marketplace Open Enrollment: November 1, 2026 – January 15, 2027
Enrollment opens: November 1, 2026
Enroll by December 15, 2026 for coverage starting January 1, 2027
Final deadline: January 15, 2027 for coverage starting February 1, 2027
The ACA marketplace open enrollment period is set by the Centers for Medicare & Medicaid Services (CMS). During this window, anyone can enroll in a marketplace plan, switch plans, or update their coverage — no qualifying life event needed. If you enroll between December 16 and January 15, your coverage won't start until February 1. To avoid any gap, enroll before December 15.
Note: Some states run their own exchanges with different dates. California (Covered California), New York, Massachusetts, Colorado, and others may extend deadlines or open enrollment earlier. Check your state exchange for exact dates.
If your employer offers ICHRA, you can use the marketplace during open enrollment — and your employer's employee health budget applies to your premium. Thatch guides you through the entire process.
Medicare Open Enrollment Dates for 2026–2027
Medicare Annual Enrollment Period (AEP): October 15 – December 7, 2026
During the AEP, Medicare beneficiaries can:
Switch from Original Medicare to Medicare Advantage (or vice versa)
Change Medicare Advantage plans
Join or drop Medicare Part D prescription drug coverage
Changes take effect January 1, 2027.
Medicare Advantage Open Enrollment Period: January 1 – March 31, 2027
If you're enrolled in a Medicare Advantage plan, you can make one plan change during this period:
Switch to a different Medicare Advantage plan
Drop Medicare Advantage and return to Original Medicare (and enroll in Part D)
Changes take effect the first of the month after enrollment.
Medigap Open Enrollment: 6 months from Part B effective date
Your Medigap open enrollment period is the 6-month window starting the month your Medicare Part B coverage begins. During this period, you can buy any Medigap policy sold in your state — regardless of health status. After this window, you may face medical underwriting.
Note: Thatch does not administer Medicare plans. This section is provided for informational completeness. If your employer offers ICHRA for non-Medicare-eligible employees, Thatch handles that enrollment separately.
Employer-Sponsored Benefits: When Is Open Enrollment?
Unlike marketplace and Medicare enrollment, employer-sponsored open enrollment dates are set by each employer. Most companies run open enrollment in October or November for January 1 effective dates, but there's no federal requirement for specific dates. Key things to know:
Your employer must give you reasonable notice before open enrollment starts
You typically have 2–4 weeks to make elections
If you don't actively enroll, your previous elections may roll over — but not always
Benefits can change year to year even if you keep the same plan
How ICHRA Changes the Employer OE Timeline: Traditional group plans lock employers into rigid renewal cycles. With ICHRA through Thatch, employers can set flexible enrollment windows — including rolling enrollment for new hires. No more scrambling to get everyone through a 2-week window. Employees choose their own plans on the marketplace or off-exchange, and Thatch handles the enrollment, carrier payments, and compliance.
2026–2027 Health Insurance Enrollment Calendar
| Enrollment type | Dates |
|---|---|
ACA Marketplace Open Enrollment | Nov 1, 2026 – Jan 15, 2027 |
Medicare Annual Enrollment Period (AEP) | Oct 15 – Dec 7, 2026 |
Medicare Advantage Open Enrollment | Jan 1 – Mar 31, 2027 |
Medigap Open Enrollment | Individual — 6 months from Part B effective date |
Employer-sponsored plans | Varies — typically Oct–Nov |
ICHRA with Thatch | Flexible — set by your employer |
Missed the Deadline? Here's What to Do
If you miss open enrollment, you may still be able to get coverage through a Special Enrollment Period (SEP). Qualifying life events include:
Losing existing health coverage (job loss, aging off a parent's plan)
Getting married or divorced
Having or adopting a baby
Moving to a new state or coverage area
Changes in income that affect subsidy eligibility
Gaining citizenship or lawful presence
You typically have 60 days from the qualifying event to enroll.
With ICHRA employers using Thatch, new hires can enroll at any time — you're not limited to the marketplace open enrollment window for employer-funded coverage.
Open Enrollment Dates FAQ
When does open enrollment start for 2027 health insurance?
ACA marketplace open enrollment for 2027 coverage begins November 1, 2026. Medicare Annual Enrollment begins October 15, 2026. Employer-sponsored enrollment dates vary by company.
When does open enrollment end?
ACA marketplace open enrollment ends January 15, 2027. The December 15 deadline is critical — enroll by then for January 1 coverage. Medicare AEP ends December 7, 2026.
Can I sign up for health insurance after open enrollment?
Only if you qualify for a Special Enrollment Period through a qualifying life event. Otherwise, you must wait until the next open enrollment period. Exception: ICHRA employers using Thatch can offer enrollment outside the standard window.
Is open enrollment the same as ACA enrollment?
ACA marketplace enrollment is one type of open enrollment. The term also applies to Medicare enrollment periods and employer-sponsored benefits enrollment. Each has different dates and rules.
What time does open enrollment start on November 1?
HealthCare.gov and state exchanges typically update at 12:00 AM Eastern Time on November 1. You can begin enrolling as soon as the site updates.
